1. Field of the Invention
The present invention relates to an optical recording medium which allows a user to record information data.
2. Description of the Related Art
Currently, a write-once type DVD (Digital Versatile Disc)-R and a rewritable DVD-RW have been commercially produced as optical recording media.
FIG. 1 is a perspective view illustrating the structure of a recording surface and a cross section of a DVD-R or a DVD-RW (hereinafter simply referred to as the xe2x80x9cDVDxe2x80x9d). FIG. 1 illustrates the configuration of the DVD before information data (audio data, video data, and computer data) is recorded thereon by an information recording/reproducing apparatus.
As illustrated in FIG. 1, convex (when viewed from the viewing point of the figure) groove tracks GV and concave (similarly when viewed from the viewing point of the figure) land tracks LD are previously formed spirally or concentrically in alternation on a recording layer R of the DVD before information data is recorded. As shown in FIG. 1, the DVD has a transparent substrate B which attaches to the recording layer R at the substrate""s surface having the groove and land tracks.
The land tracks LD are provided with a plurality of previously formed land prepits LPP which serve as addresses for recognizing particular positions on the groove tracks GV and as recording timing. Each of the land prepit LPP is formed to connect two adjacent groove tracks GV, and its bottom surface (indicated by hatching) is continuous with the bottom surfaces (similarly, indicated by hatching) of associated groove tracks GV.
An information recording/reproducing apparatus for recording information data on the DVD as mentioned above reads the land prepits LPP from the DVD to recognize the position above a particular groove track GV, and irradiates the groove track GV with recording beam light in accordance with information data. In this process, heat is conducted to a region irradiated with the recording beam light to form information pits PT in that region as illustrated in FIG. 2.
However, when the recording beam light from the DVD recorder is irradiated to a position including a land prepit LPP on a groove track GV, deformed information pits are formed such as information pits PT1, PT2 illustrated in FIG. 2. This is because the heat generated when the recording beam is irradiated also affects a portion of the land prepit LPP.
Thus, when information data is reproduced from the DVD having a recording configuration as illustrated in FIG. 2, waveform distortion can occur in a read signal generated by reading the above-mentioned deformed information pits PT1, PT2, resulting in a higher read error rate.
The present invention has been made in view of the problem mentioned above, and its object is to provide an optical recording medium which is capable of producing a read signal free from waveform distortion when information is reproduced therefrom.
An optical recording medium according to the present invention comprises groove information tracks on which information pits carrying information data are to be formed, and land prepit tracks provided with a plurality of previously formed land prepits connected to the groove information track, wherein the groove information tracks and the land prepit tracks are arranged in alternation. The groove information track has a smaller track width in at least a part of each of sections in which the land prepit exists than in sections in which no land prepit exists.